Closure for plastic packaging containers

ABSTRACT

The present invention relates to a closure for plastic packaging containers that exhibits innovative features that can simplify the manufacturing process and the filling with liquid and viscous products, but the main effect of which is to prevent the package walls from collapsing following a change in vapour pressure inside the container, regardless of the filling temperature.

FIELD OF THE INVENTION

This invention comprises a lid for plastic packs, especially thermo-formed cup-type packs that are commonly used for containing liquid products and ready-to-drink beverages, such as teas, fruit drinks etc. The lid addressed by this invention is endowed with innovative technical characteristics that prevent the collapse of such packs.

Additionally, this invention addresses a lid for plastic packs that comprises a structure endowed with a configuration that can allow sterilization during hot filling operations (up to 92° C.) with high acidity pastes or liquids (pH<4.5), thus eliminating the use of preservatives for the storage, distribution and sale of such products at room temperature. Furthermore, through eliminating the effect of the collapse of the pack, this allows these packs to be stacked and displayed on sales gondolas in an appropriate and safe manner.

GROUNDS FOR THE INVENTION

Thermo-formed cup-type plastic packs are commonly used on the Brazilian market for liquid products, especially low value-added ready-to-drink beverages, consisting of a plastic cup whose open end is closed with a seal-type lid in the form a flat sheet.

Normally, this lid consists of a layer of aluminum and another of polyethylene, with the latter allowing it to be thermo-welded to the rim of the cup.

As known to technical experts in this matter, the market requires that the final cost of these products be relatively low. As a result, companies are seeking solutions that reduce fabrication expenditures as much as possible, particularly for secondary items such as packs, labels and lids, for example. Along these lines, as a common practice in these companies, the packs are produced with the smallest possible amount of material, resulting in a light, thin product, normally using what are known as thermo-moldable polymers, which are the cheapest raw materials.

However, for beverages with lower added value, reducing the thickness of the walls of these packs quite logically results in less rigidity and more flexibility for their structure.

As a result, it is noted that during the fabrication and filing process of these beverages, this fragility adversely affects the structure of the final product, and may result in the collapse of the pack walls after the lid has been placed in position and the beverage has cooled.

More specifically, these beverages are at temperatures of around 30° C. during regular filling processes, and closing the pack with a lid results in an inner space containing air between the surface of the beverage and the inner face of the lid, also known as head space.

With the drop in the temperature of the product in the refrigerator, a vacuum forms in the pack, caused by the shrinkage in the volume of the beverage and a reduction in vapor pressure in this headspace region. Thus, as is known to technical experts in the matter, for this type of pack and packaging for liquid products, there is no way of offsetting this vacuum without weakening the pack structure. Consequently, due to a natural effect, attempts are made to offset this in the weakest parts, which may result in the partial collapse of the pack walls, as they are less rigid, being thinner and more flexible, as mentioned above.

This collapse effect increases as the temperature of the filled beverage rises: the higher the filling temperature, the more severely the pack walls collapse as the beverage cools, meaning that sterilization through hot bottling (up to 92° C.) is impractical for this type of pack. Consequently, it is important to stress that bottling at temperatures below 60° C. does not sterilize the beverages, meaning that preservatives are required for their storage, distribution and sale at room temperature. In today's world, when health and good nutrition are increasingly more important in the lives of human beings, the use of preservatives is viewed and considered as being harmful to health.

Additionally, it is known that the collapse of these packs causes a series of problems for the logistics, packaging and sale of the end product. This is because a ‘crushed’ pack is normally viewed as being a product with problems, or old, meaning that consumers normally refuse to purchase a product when it is crushed or collapsed.

This is also a sales gondola display problem as, depending on the extent to which the pack has collapsed, it may be distorted; as a result, it will be difficult to stack or display one pack over another on the sales gondolas. This problem is relatively critical for supermarkets, hypermarkets and markets in general, as gondola stacking must be optimized to the greatest possible extent, using the least possible space to display the largest variety of products. Consequently, if state-of-the-art packs are subject to this collapse effect, becoming irregular, they cannot be stacked, and consequently they must be displayed at a single level.

In another situation, such as cream cheese, for example, which is necessarily thermo-processed (up to 92° C.) as the packs are filled by heat-treating the product, partial solution was to use injected plastic cups with thicker and more resistant walls. Although they are far more expensive than the thermo-shaped plastic cups used for low value added ready-to-drink beverages, they are still less expensive than traditional glass packs.

It is thus important to stress that injected plastic packs would make low value added ready-to-drink beverages too expensive, while at the same time the thermo-shaped plastic packs known as the state of the art do not allow hot processing while filling packs with products such as cream cheese.

In other words, in order to avoid the collapse of packs containing low value added ready-to-drink beverages, it would be necessary to use heavier injected plastic packs which would not be economically feasible, while hot-processing products in thermo-formed plastic packs is also not feasible in practice, as the packs would collapse. Consequently, there are clear constraints currently in place on the filling and sale of specific consumer goods.

In order to resolve some of the inconvenient aspects listed above, a thermo-formed cup-type pack is shown that was developed in order to avoid the collapse of the structure after the pack is filled and closed. This pack comprised a type of valve at the bottom of the cup body; more particularly, this bottom was intended to retract when a vacuum formed in the cup. However, this configuration did not prove effective, as an expensive cup fabrication process was required, using specific high-precision equipment for shaping the pack bottom.

In practice, it was also noted that the adverse effects remained for the flexibility and rigidity of the walls of the cup structure, which in fact continued to collapse even before the above-mentioned valve was tripped into action. The possible alternative of increasing the wall thickness undermined the economic feasibility of the pack, and consequently the end product, for low value added ready-to-drink beverages.

Consequently, it is quite clear that, although functional so far, these packs, especially thermo-formed cups for low value added ready-to-drink beverages, offer some inconvenient aspects and limitations, related mainly to the quality of the pack structure, intervening negatively in the configuration and appearance of the end product.

BRIEF DESCRIPTION OF THE INVENTION

Consequently, the purpose of this invention comprises a lid for thermo-formed plastic packs for packaging pastes and liquid products, preferably similar to cream cheeses and ready-to-drink beverages, which manages to resolve all the inconvenient aspects apparent in the state of the art as mentioned above, in a simple, safe and efficient manner.

More preferably, the purpose of this invention is to provide a lid for thermo-formed plastic packs with a configuration that can efficiently avoid the collapse of the walls of the pack as the end product cools after it has been filled and sealed, regardless of the beverage filling temperature.

Additionally, another purpose of this invention is a lid for plastic packs that allows sterilization while filling with (up to 92° C.) hot high acidity (pH<4.5) beverages, with no need for preservatives.

Another purpose of this invention is a lid for thermo-formed cup-type plastic packs that ensures the integrity of the entire structure, meaning that the original appearance is maintained, allowing better displays, including the stacking of these packs on sales gondolas, in order to fine-tune their fabrication and transportation logistics, as well as displays for sale.

Yet another purpose of this invention is a lid for cup-type and pot-type thermo-formed and injected plastic packs that can resolve the problems caused by the collapse of the walls thereof due to the formation of inner vacuums in a simple, low-cost manner, with no need for reformulating either their materials or sizes.

These and other purposes, effects and advantages offered by the lid addressed by this invention are achieved through the configuration developed and applied to the structure that comprises the lid. As set forth in this invention, the lid comprises a structure that efficiently assures the structural integrity of the body of the packs, regardless of the condition of beverage during and after filling, closing and cooling of the end product.

Consequently, a preferential purpose of this invention is a lid for plastic packs that comprises a sheet with a plurality of ridges and grooves in a corrugated format, surrounding at least part of the surface of such sheet, with such ridges and grooves having ends that may be curved to a greater or lesser extent.

It must also be made clear that the quantity and height of the ridges and grooves arrayed this sheet vary according to the type of beverage and fabrication and filling process thereof. More particularly, they are larger and higher for beverages that are hotter during the filling process.

Preferably, this sheet consists of a layer of aluminum covered by a layer of polyethylene, polypropylene or thermo-sealing varnish that allows such lid to be heat-welded to the rim of the plastic pack.

BRIEF DESCRIPTION OF THE FIGURES

These and other purposes, technical effects and advantages of the lid for the thermo-formed plastic packs encompassed by this invention will be clear to technical experts in the matter, through the appended schematic figures, which illustrate preferred, but not limiting, realizations of this invention, as follows:

FIGS. 1A, 1B, 1C and 1D schematically present the lid and the closed, thermo-sealed plastic pack, as constituted by the state of the art;

FIGS. 2A and 2B schematically present two preferred realizations of the pack lid, as addressed by this invention;

FIG. 3 schematically presents a thermo-sealed plastic pack closed by a lid, as addressed by this invention, particularly after filling with beverages at a conventional temperature;

FIG. 4 schematically presents the closed pack illustrated in FIG. 3, now cooled;

FIG. 5 schematically presents a thermo-sealed plastic pack closed by a lid in an alternative realization of this invention, particularly after filling with a beverage at a high temperature;

FIG. 6 schematically presents the closed pack illustrated in FIG. 5, now cooled;

FIGS. 7 and 8 show side views of the lids as addressed by this invention under different beverage volume and vapor steam pressure conditions, after closing the plastic packs.

DETAILED DESCRIPTION OF THE INVENTION

Initially, it must be reiterated that the lid for plastic packs addressed by this invention will be described below according to preferred realizations that are not limiting, as its application may be valid for different packs and for packaging different products presenting variations in the vacuum resulting from the reduction in the product volume and its vapor pressure while cooling after filling during the fabrication process or through the consumption of O₂ in the air found in the pack through oxidation reactions during the useful life of the product.

Merely as an illustration, FIGS. 1A to 1D illustrate conventional realizations of a lid and pack as known in the state of the art. FIG. 1A shows a lid 1 comprising an aluminum sheet and a layer of polyethylene, polypropylene or thermo-sealing varnish. As illustrated in FIG. 1B, the above-mentioned lid 1 is placed on the open end 3 of the pack 2 after it is filled with a beverage 4 at a temperature of around 30° C. to 35° C.; this lid 1 is then heat-welded to the rim of the above-mentioned pack 2, leaving it ready for sale.

However, as mentioned previously, these closed packs are subject to reductions in temperature, frequently reaching around 10° C. or less, when in a refrigerator or cooling unit. Due to this reduction in temperature, the volume of the product and its vapor pressure also drop, resulting in the formation of a vacuum in the head space 5 holding air in the pack. Consequently, in an attempt to offset this reduction in the product volume and the drop in its vapor pressure, with a consequent reduction in the head space volume, the walls of the body of the pack 2 are subject to collapse 6, as illustrated in FIG. 1C.

FIG. 1D illustrates the more critical situation, in which beverage 4 was filled at a high temperature of around 92° C. and then cooled to a temperature close to 10° C. In this case, the collapse is more severe and causes even more problems in structural and visual terms, resulting in inconvenient aspects for the logistics of the end product.

Now referring to FIGS. 2A and 2B, which illustrates two preferred realizations of the lid, according to this invention, it is noted that the surface of the above-mentioned lid 10 is extended with concentric corrugations, meaning through ridges and grooves 11 that surround the entire lid structure. Preferably, these ridges and grooves 11 comprise a corrugated format, meaning a sequence of corrugations in a pleated section.

Even more preferably, the configuration of the above-mentioned ridges and grooves 11 may vary according to the type of beverage and its fabrication and filling process, meaning the quantity and/or height of the corrugations may be increased or decreased, depending on the properties of the liquid or product in the pack. In other words, depending on the processing conditions, with or without heat-sterilization of the beverage, the number and/or height of the ridges and grooves 11 may be greater or lesser, meaning that the corrugated configuration may be higher and/or longer and lower and/or shorter.

FIGS. 3, 4, 5 and 6 illustrate two preferred realizations of the elongated lid 10 according to this invention, closing a thermo-formed plastic pack 2 holding a beverage 4. More specifically, the realization presented in FIGS. 3 and 4 simulates a conventional beverage processing and filling system, although using the elongated lid 10 in question. In this realization, the liquid was filled at a temperature close to 30° C., which did not result in drastic variations in the configuration of the pack 2, nor in the elongated lid 10. However, when sealed pack 2 is placed at a temperature of around 10° C., it is noted that the volume of the liquid drops, with a reduction in its vapor pressure in the head space 5 and, in a response that offsets such effects, this corrugated configuration of the ridges and grooves 11 extends, filling part of the head space 5. As may be noted, the body of pack 2 remains unaltered, with no indication of the collapse of its walls.

In the realization illustrated in FIGS. 5 and 6, an elongated lid 10 was used whose corrugated configuration of ridges and grooves 11 is larger, meaning that it presents a larger number of corrugations. In this case, the parameter for the simulation was the sterilization of the beverage during the fabrication and filling process, meaning the elimination of the use of preservatives. As may be noted, when closing pack 2 with elongated lid 10, due to the increased vapor pressure in the head space 5, elongated lid 10 stretches positively. When cooling, with a lower beverage volume and a reduction in its vapor pressure in the head space 5, the elongated lid 10 retracts and shrinks negatively, resulting in the corrugated configuration of the ridges and grooves 11 being eliminated in the head space 5, thus offsetting the above-mentioned reduction in the beverage volume and the drop in its vapor pressure.

This corrugated configuration of ridges and grooves 11 may be better understood through FIGS. 7 and 8, which present comparative illustrations of the extension levels of the surface of elongated lid 10, both positively and negatively.

More specifically, as illustrated in FIGS. 7 and 8, it is noted that the natural status of elongated lid 10 is at level (0), with the ridges and grooves 11 apparent; after filling and closing the pack, the high temperature of the filled beverage increases the product volume and its vapor pressure in the head space 5; as a result, the above-mentioned elongated lid 10 stretches positively, whereby the corrugated configuration begins to vanish, resulting in a flat configuration, as shown by levels (+1, +2, +3, +4).

While cooling, the product volume and its vapor pressure in the head space start to shrink and consequently, the above-mentioned elongated lid 10 begins to retract, then stretching negatively in order to offset the space resulting from the reduction in the product volume and the drop in its vapor pressure in the head space, reaching the respective levels (−1, −2, −3, −4) and avoiding the risks of the pack wall collapsing.

It is important to stress that, although the illustrations and descriptions presented above mention a circular cup-type pack, there is nothing preventing this lid from being applied to packs of different shapes, for example: rectangular, triangular, elliptical, etc.

Thus, it is stressed that the lid, as addressed in this invention, can resolve a series of inconvenient aspects caused by plastic pack lids constituting the state of the art, particularly with regard to pack integrity.

Furthermore, it is possible to upgrade the fabrication process in beverage plants, as this allows the beverage to be heat-sterilized while filling, meaning that no preservatives are required for these products.

As well understood by technical experts in the matter, there are many possible modifications and variations of this invention in the light of the explanations presented above, without moving beyond the scope of its protection, as demarcated in the appended Claims. 

1. A lid for a plastic pack comprising a sheet with a plurality of ridges and grooves in a corrugated format that surround at least part of the surface of the sheet.
 2. The lid for a plastic pack according to claim 1, wherein the ridges and grooves in the corrugated format are endowed with curved ends.
 3. The lid for a plastic pack according to claim 1, wherein the number and height of the ridges and grooves varies, depending on type of product and its fabrication and filling processes, being larger when stronger vacuums are formed due to the product filling temperature as well as product oxidation reactions during the useful life thereof.
 4. The lid for a plastic pack according to claim 1, wherein the sheet comprises a layer of aluminum covered by a layer of polyethylene, polypropylene or thermo-sealing varnish.
 5. Plastic packaging comprising the lid according to claim
 1. 6. The lid for a plastic pack according to claim 2, wherein the sheet comprises a layer of aluminum covered by a layer of polyethylene, polypropylene or thermo-sealing varnish.
 7. The lid for a plastic pack according to claim 3, wherein the sheet comprises a layer of aluminum covered by a layer of polyethylene, polypropylene or thermo-sealing varnish.
 8. Plastic packaging comprising the lid according to claim
 2. 9. Plastic packaging comprising the lid according to claim
 3. 